Fibrillated yarn carpet backing



Dec. 22, 1970 E. F. GREENWALD ETA!- 3,549,470

FIBRILLATED YARN CARPET BACKING Filed Jan. 5, 1967 EXTRUDE FOAMED THERMOPLASTIC RESIN FIBRILLATE BY HOT- MELT ATTENUATION DRAW TAKE UP FIBRILLATED YARN WEAVE OR KNIT fiig 2. INVENTORS EMMETT E GREENWALD RICHARD A. KENNEY ATTORNEY United States Patent 3,549,470 FIBRILLATED YARN CARPET BACKING Emmett F. Greenwald and Richard A. Kenney, Charlotte, NC, assignors to Celanese Corporation, New York,

N.Y., a corporation of Delaware Filed Jan. 3, 1967, Ser. No. 606,573 Int. Cl. B32b 5/16 US. Cl. 161-70 4 Claims ABSTRACT OF THE DISCLOSURE A process for the preparation of a carpet backing and the product produced thereby, the process comprising hot-melt attenuation foam fibrillating a thermoplastic extrudate to strand form, and then formulating the strands into a backing fabric.

This invention relates to fibrillated yarn fabrics, and more specifically to fibrillated yarn fabrics suitable for use as carpet backings.

Carpet backings may be divided into primary and secondary carpet backings. The primary backing is the support or underside of the carpet which secure the pile yarns in position and provides a firm foundation. The secondary backing is used in the preparation of tufted carpets and is secured to the pile carrying primary backing in order to give the carpet added strength and dimensional stability; that is to say, the ability to resist stretching and shrinking.

Both primary and secondary carpet backings are commonly prepared from flat woven burlap materials prepared from jute and sisal. Fabrics of this type however, when employed as primary backings are deficient in their thickness which reduces the amount of face yarn in the pile, in their heavy weight and to some extent, lack of dimensional stability. Perhaps the most serious deficiency of jute and sisal primary carpet backings is their lack of uniform thickness and lack of uniform density. This characteristic is due in part to the actual interstices between the individual yarns and in part to the wide variations in the same yarn. As a result, in carpet tufting operations the tufting needles employed in tufting face yarns through the carpet backing may either meet no resistance due to voids, or at the other extreme, encounter maximum resistance due to the necessity for penetrating thick, or double yarns. In still other instances, the tufting needles push aside the backing yarns with little or no penetration of the backing yarn itself. As a result, the rows of pile yarn stitches frequently jump back and forth between the same longitudinal yarns in the backing, thus causing gaping and/or crowding between adjacent rows of stitches. This phenomenon, which is known as needle deflection, results in pattern deformation and grin through, that is to say, an exposure of the backing by the uneven rows and consequently poor coverage of the pile yarns.

In addition to these mechanical difliculties inherent in primary carpet backings produced from jute and sisal, the aformentioned materials also have certain degradation deficiencies. These chemical deficiencies manifest themselves in the high moisture absorbency and in the inability of the aforementioned materials to withstand weathering conditions. Most recently, carpets which have the ability to be employed both indoors and outdoors have gained wide acceptance. It is, of course, a prerequisite for outdoor use, that the carpet, that is to say, both the carpet face pile and the carpet backing both primary and secondary, be non-absorbent, free from mildew and dry rot odor and able to withstand Weathering conditions without stretching or shrinking.

3,549,470 Patented Dec. 22, 1970 While carpet backings are available which have satisfactory resistance to outdoor weathering conditions, these carpet backings which are commonly produced from thermoplastic ribbons still exhibit a deficiency in tufting and needle deflection as well as dimensional stability.

It is therefore, an object of this invention to provide a woven carpet backing which is resistant to outdoor weathering conditions and which exhibits minimal needle deflection.

It is another object of this invention to provide a woven carpet backing which is durable to outdoor weathering conditions and which exhibits enhanced dimensional stability.

It is an additional object of this invention to provide a process for the preparation of a carpet backing having enhanced physical characteristics and durability to outdoor weathering conditions.

In accordance with this invention, it has now been discovered that a product suitable for use as carpet backing may be obtained by constructing a fabric from a foam fibrillated yarn, the construction being a woven or a knitted construction. Where the yarn employed is a polypropylene yarn, the fabric is preferably heat stabilized and if the fabric application is a primary carpet backing, the fabric is also subjected to a calendering operation. Fibrillated polymeric yarn is produced by a process which consists of producing an extrudate from a mixture comprising a molten polymer and a foaming agent which is or evolves gas at extrusion temperature and then drawing the extrudate. The molten extrudate is preferably hotmelt drawn or attenuated at temperatures above the glass transition temperature of the polymeric material. After stretching of the hot melt attenuated product, it is preferred to orient the polymer and thereby produce increased strength. It is also preferred that the melt, in addition to containing a foaming agent, also contain a coloring component, that is to say, it is preferred that the extrudate be a dope dyed extrudate. In the event that a fabric suitable for piece dyeing is contemplated, it is preferred that the extrudate, such as for instance a polypropylene extrudate contain a dye receptive component.

A better understanding of the invention may be had from the drawings wherein:

FIG. 1 is a photograph of the carpet backing of this invention having 1200 denier filament fibrillated polypropylene warp and fill yarns woven so as to have 14 ends and 10 picks perinch;

FIG. 2 is a flow sheet of the process sequence for the preparation of the carpet backing of this invention.

The present invention is applicable to all thermoplastic resins which can be fabricated by melt extrusion. Suitable resins include one or more polymers and/or copolymers of materials such as polyethylene, polypropylene, polybutene, polymethyl-3-butene, polystyrene, polyamides such as polyhexamethylene adipamide and polycaprolactam, acrylic resins such as poly methylmethacrylate and methyl methacrylate, polyethers such as polyoxymethylene, halogenated polymers such as polyvinyl chloride, polyvinylidene chloride, tetrafluoroethylene, hexafluoropropylene, polyurethanes, cellulose esters of acetic acid, propionic acid, butyric acid and the like, polycarbonate resins and polyacetal resins. Resins which have been found to be especially suitable for use in conjunction with the present invention are polyethylene, poly propylene, polystyrene and polymethyl-3-butene.

The foaming agents which are useful in the extrusion of foam are known. As previously indicated, solids or liquids which vaporize or decompose into gaseous products at the extrusion temperatures, as well as volatile liquids, may be employed. Solids which are suitably employed in the "ice process of the present invention include azoisobutyric dinitrile, diazoamino benzene, 1,3 bis (p-xenyl) triazine azodicarbonamide and similar azo compounds which decompose at temperatures below the extrusion temperature of the forming composition. Commonly used solid foaming agents producing either nitrogen or carbon dioxide include sodium bicarbonate and oleic acid, ammonium carbonate and mixtures of ammonium carbonate and sodium nitrite. Volatile liquids which are suitable foaming agents include acetone, methyl ethyl ketone, ethyl acetate, methyl chloride, ethyl chloride, chloroform, methylene chloride, methylene bromide and, in general, fluorine containing normally liquid volatile hydrocarbons. Foaming agents which are the normally gaseous compounds such as nitrogen, carbon dioxide, ammonia, methane, ethane, propane, ethylene, propylene and gaseous halogenated hydrocarbons are also desirable. A particularly preferred class of foaming agents are fluorinated hydrocarbon compounds having from 1 to 4 carbon atoms which, in addition to hydrogen and fluorine, may also contain chlorine and bromine. Examples of such blowing agents are:

dichlorodifluoromethane; dichlorofluoromethane; chlorofiuoromethane; difluoromethane; chloropentafiuoroethane; 1,2-dichlorotetrafluoroethane;

1, 1-dichlorotetrafluoroethane;

1, 1,2-trichlorotrifluoroethane;

1, l,1-trichlorotrifluoroethane; 2-chloro-1,1,1-trifiuoroethane; 2-chloro-1,1, 1 ,2-tetrafluoro ethane; 1-chloro-1,1,2,2-tetrafiuoroethane; 1,Z-dichloro-1,1,2-trifluoroethane; l-chloro-1,1,2-trifluoroethane; l-chloro-l,l-difluoroethane; perfluorocyclobutane; perfluoropropane; 1,1,1-trifluoropropane; l-fluoropropane;

2-fiuoropropane; 1,1,1,2,2-pentafluoropropane;

1, l,1,3,3-pentafluoropropane; 1,1,1,2,3,3-hexafluoropropane; 1,1,1-trifluoro-3 chloropropane; trifluoromethylethylene; perfiuoropropene and perfluorocyclobutene.

The quantity of foaming agent employed will vary with the density of foam desireda lower density requiring a greater amount of foaming agentthe nature of the thermoplastic resin foamed and the foaming agent employed. In general, the concentration of the foaming agent will be from 0.001-5 lb./moles 100 lbs. of the thermoplastic resin.

Fibrillated products prepared by the hot melt attenuation technique contain individual fibrils, the cross-sections of which are irregular in shape and size and substantially devoid of planar surfaces. It should also be noted that within the same fibril there will be a plurality of geometrically different cross-sections. Preferably, the fibrillated product employed in the preparation of the woven carpet backing of this invention is a fibrillated product which is extruded in film form, subsequently slit to ribbons of textile dimensions and the ribbons then worked by means of suitable mechanical agitations, so as to produce additional fibrillation. The film forming die is preferably such as to have an opening thickness of from 0.02 inch to 0.04 inch and most preferably from 0.02 inch to 0.03 inch.

A better understanding of the type of fibrillated yarns which are employed may be had from the following specific examples:

EXAMPLE A Polypropylene polymer pellets (marketed by Hercules Company under the trademark Profax) 1.7 intrinsic viscosity are dry-blended with 1% of azodicarbonamide blowing agent and sufficient quanties of D1920 Carbon Black FPP (25% pigment in polypropylene) marketed by Hercules Company to give a pigment concentration in the end product of 0.25%. Blending is carried out in a tumbling vessel for fifteen minutes. The blended polymer is then loaded into an extruder having a chrome-plated single fluted uniform pitch screw, the extruder being fitted with a die of the horizontal ribboned type having a 1" x 0.020" slit. The die is equipped with a 500 watt electric band heater. The polymer is extruded at a throughput rate of 2.5 grams per minute. The extruded sheet is maintained at temperatures above the glass transition temperature by means of a quench fork, the quench fork having tubes disposed on either side of the extruded film. The tubes have air orifices disposed therein, said orifices having a diameter of 0.04", the orifices being spaced 0.125 apart, each tube containing two rows of orifices apart. The extruded film is passed over a first roll at a speed of 25 to 35 meters per minute. At this point, a fibrillated product is obtained which is in a substantially undrawn, unoriented condition. The undrawn, unoriented fibrillated polypropylene material is then subjected to a drawing operation, the drawing operation being carried out by passage over a shoe heated to 130 C. and then taking the yarn over a roll having a winding speed of 50 to meters per minute, thereby producing a draw ratio second roll speed first roll speed second roll speed first roll speed of from 1.5 to 2, e.g., 1.7, is maintained. The tensile properties of the yarn which is produced by this process are given in the table appearing hereinafter designated as Table II.

TABLE I.TENSILE PROPERTIES OF FIBRILLATED POLY- PROPYLENE YARN Zero t.p.i.* 5 t.p.i.*

Denier 360 360 Elongation, percent 17 38 Tenacity, g./d 2. 5 3. 4 Modulus, g./d 33 23 Turns per inch.

TABLE II.TENSILE PROPERTIES OF FIBRILLATED POLYPROPYLENE YARN [Extruded-drawntwisted (5 t.p.i.)redrawn] ity, g./d Modulus, g./d

EXAMPLE B Profax polypropylene (marketed by Hercules Company), having an intrinsic viscosity equal to 1.7 is blended with 1% azodicarbonamide blowing agent and sufficient quantities of D1724 Monarch Blue FPP (25% pigment in polypropylene) marketed by Hercules Company to give a pigment concentration in the end product of 0.15%. The blended mix is then placed in a National Rubber Machinery extruder employing a screw 12" long and 1" in diameter. The extruder is equipped with a die for vertical extrusion, the die having a circular opening which is in length and /3 in diameter. The rear temperature area or Zone 2 is also maintained at 210 C. While the die-head is maintained at a temperature of 240 C. The hot-melt is extruded into a water quenching bath, the die-head being disposed 10" above the surface of the Water. The extrudate, upon contacting water is cooled to a temperature below the glass transition temperature of polypropylene and is then passed under a snubbing pin disposed beneath the surface of the water in order to attenuate air voids in the extrudate. The extrudate is then withdrawn from the water quenching bath and passed over a series of godet wheels at a takeup speed of 200 meters per minute whereby the polypropylene is oriented. The oriented material is then led around a series of pins which are disposed so as to force the extrudate to travel through a tortuous path and thereby induce fibrillation. The fibrillated product is then taken upon a suitable tape-up package.

Fibrillated yarn prepared according to Examples A and B may then be formulated into woven fabrics comprising all polypropylene yarns or blends of polypropylene yarns and yarns, such as for instance, jute, paper, cotton, rayon and various other synthetic polymeric materials. A better understanding of the precedure employed for formulating the fibrillated yarns into woven products suitable for use as carpet backings may be had from the following examples.

While the fibrillated yarn fabric of this invention is not limited to any specific construction, whether knitted or woven, the fabric is preferably prepared from yarns having a denier range of from about 800 to about 2400. If polypropylene yarn is being employed and the fabric is to be used in carpet applications, a fabric heat setting operation is preferable. The preferred heat setting range for foam fibrillated polypropylene yarn is 260 F. to 300 F. for a period of from about seconds to about 90 seconds. Where the foam fibrillated yarn fabric is to be,

employed as a primary carpet backing, it is preferred that the fabric be subjected to a calendering operation at pressures of from about 300 to about 500 pounds per linear inch at a temperature of from about 260 F. to about 300 F. The calendering operation reduces the thickness of the fabric and renders it suitable for use as a primary backing, an application wherein it is desirable to minimize quantities of pile yarn locked in the backing. Where the foam fibrillated yarn fabric is to be employed as a secondary backing, the calendering operation may be omitted; however, it is essential that the fabric be of a construction which has a porosity sufficient to allow for curing of a latex coating.

EXAMPLE I 1200 denier foam fibrillated polypropylene yarn prepared according to the process set forth in Example A and the yarn employed as warp yarn is given 0.5 turn per inch S twist. The foam fibrillated polypropylene yarn employed in both of the warp and fill is then woven to a fabric having a 14 ends x 10 picks per inch construction on the loom. The fabric is then subjected to a heatsetting operation at about 290 F. for a time of about one minute. The heat-set fabric is then calendered at a pressure of 500 pounds per linear inch at a temperature of about 280 F. The fabric is found to have a final construction of 15 ends x 11 picks per inch. The fabric is found to have satisfactory grab tensile strength, satisfactory stiffness and satisfactory porosity. When the poly propylene carpet backing is compared with a corresponding jute control it is found that the polypropylene carpet backing produces one-half the needle deflection of the jute control.

EXAMPLE II 1200 denier foam fibrillated polypropylene yarn is prepared according to the process set forth in Example B and the yarn employed a warp yarn is given 0.5 turn per inch Z twist. The polypropylene yarn employed in both the warp and the fill is then woven to a fabric having a 14 x 13 construction on the machine. The fabric is then subjected to a heat setting operation at a temperature of 300 F. for a period of about one minute. The heat set fabric is then calendered at a pressure of 600 pounds per linear inch at a temperature of about 280 F. The resultant fabric is found to have satisfactory grab tensile strength, satisfactory stiffness and porosity and to exhibit only half the needle deflection of a corresponding jute control.

EXAMPLE III The fibrillated polypropylene product as described in Example A is formulated into a 1200 denier yarn. The foam fibrillated polypropylene yarn is used as a fill yarn and 3.55 paper yarn (cotton count) prepared from 20 pound kraft paper having 5 /2 turns per inch is used as the warp yarn, the product being woven so as to have the 14 x 10 construction in the machine. The fabric is then subjected to a calendering operation carried out as a pressure of 500 pounds per linear inch at a temperature of 280 F. The resultant product is found to have satisfactory grab tensile strength, satisfactory rigidity, satisfactory porosity and a degree of needle deflection which is less than that exhibited by a corresponding jute control.

Having thus disclosed the invention, what is claimed is:

1. A carpet backing comprising a structure selected from the group consisting of woven structures and knitted structures having all fibrillated polymeric yarns produced by hot-melt attenuation foam fibrillation whereby the individual fibrils of said yarns have cross-sections which are irregular in shape and size and substantially devoid of planar surfaces.

2. The product of claim 1 wherein said fibrillated polymeric yarns are polymeric materials selected from the group selected from the group consisting of polyethylene, polypropylene, polyamide, polyester, polystyrene and combinations thereof.

3. The product of claim 1 wherein said fibrillated polymeric yarns are dope dyed fibrillated polymeric yarns.

4. The product of claim 1 wherein said polymeric material is polypropylene.

References Cited UNITED STATES PATENTS 2,948,927 8/1960 Rasmussen 28-1UX(.4) 3,003,304 10/1961 Rasmussen 28--1UX(.4) 3,210,239 10/1965 Ebere et al 291UX(.4) 3,227,664 1/1966 Blades et al 281UX(.4) 3,227,794 1/ 1966 Anderson et al. 28-1UX(.4) 3,283,788 11/1966 Bottomley et al. 281UX(.4) 3,227,784 1/1966 Blades et al. 26453 3,277,221 10/1966 Parrish 264-53 3,403,203 9/1968 Schirmer 264-51 3,405,516 10/ 1968 Laureti 57144 FOREIGN PATENTS 1,114,151 5/1968 Great Britain 28-1(F) LOUIS K. RIMRODT, Primary Examiner US. Cl. X.R. 

